Analysis of technological processes of production of spherical powders and granules of NiAl nickel monoaluminide for the needs of domestic engine building

Abstract

The article is devoted to the study of the features of various methods for obtaining granules of nickel aluminide NiAl. The problems hindering the widespread use of nickel aluminide NiAl in modern aircraft and engine construction are analyzed. It has been revealed that the main problems hindering the widespread industrial use of nickel aluminide NiAl are practically zero plasticity of the material during pressure treatment and difficulties in machining parts made of this material. However, this problem can be solved with the use of pellet metallurgy technologies, when by sintering the granular material, an almost finished product is obtained that requires minimal amounts of subsequent machining. Within the framework of the conducted studies, the quality criteria of the obtained granules were determined, which include the sphericity of the granules, the stability of the obtained dimensions of the granular material, the absence of defects in the form of pores, the absence of satellites on the surface of the granules, the presence of a finely dispersed dendritic structure of the granule material. Several methods of obtaining granules of nickel aluminide NiAl have been investigated from the point of view of obtaining the highest quality raw materials, namely: the method of spraying the melted billet with a high-temperature inert gas flow (gas atomization method), the method of centrifugal spraying of the melted electrode (PREP method), the method of centrifugation of the melt using a perforated crucible. It is determined that the optimal way to obtain a high-quality granulate of NiAl material is the method of centrifugal spraying of the melted electrode. In the course of the conducted research, it was proved that the main parameter of the process of centrifugal spraying of the melted electrode, affecting the quality of the obtained granules, their diameter and the value of the dendritic parameter of the microstructure of the granules, is not so much the current strength I as the rotation speed of the melted electrode n. The optimal values of the electrode rotation speeds are determined, which are n ≈ 15000-16000 revolutions per minute at a current strength I ≈ 1000-1500 A. A technology for obtaining high-quality NiAl material granulate has been developed and tested, which includes operations for obtaining initial NiAl blanks by self-propagating high-temperature synthesis, subsequent remelting of semi-finished products, heat treatment, separation of granules and subsequent granulation by the PREP method.